Japanese Patent Application Laid-open Publication No. 2013-058473 discloses a storage apparatus with a redundant disk array unit, in which a first disk-array control unit is capable of using a cache memory of a second disk-array control unit.
In recent years, a storage system which can extend the capacity and the performance by performing addition and exchange of a storage node (grid storage system) has been proposed. Such storage system stores data in a state that the data is distributed in a plurality of storage nodes. Also, generally, such storage system is often designed so that data may be stored equally to a plurality of storage nodes in order to give consideration to performance and fault tolerance.
For example, Patent document 1 discloses a technology about a distributed storage system including a plurality of interface processors and a plurality of storage devices. Specifically, Patent document 1 discloses a technology in which an interface processor and a storage device store a node list including an IP address of at least one storage device and an interface processor controls a storage device based on the node list.
Patent document 2 discloses a technology about a distributed file system including a data relocation processor. Specifically, Patent document 2 discloses a technology which calculates a relocation position of data of a file for which relocation of data is uncompleted and exchanges data between each storage node based on the calculation result.
Meanwhile, as an example of a technology about parity for detecting erroneous data, Patent document 3 discloses a technology about data reading processing in a receiving device of a data broadcasting system. Specifically, Patent document 3 discloses a technology in which a judgment is performed based on data read by a receiving device, and, when the data which has been read is normal data, data about parity that is unnecessary is not read.    [Patent document 1] Japanese Patent Publication No. 4696089    [Patent document 2] Japanese Patent Application Laid-Open No. 2010-238038    [Patent document 3] Japanese Patent Application Laid-Open No. 1998-107748